1. Field of the Invention
The present invention relates to an optical film, a polarizing plate, and a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device with high light transmittance and high color reproducibility; an optical film used for this liquid crystal display device; and a polarizing plate using this optical film.
2. Description of the Related Art
The application of a flat panel display such as a liquid crystal display device (hereinafter, also referred to as an LCD) is widened as a space-saving image display device with low power consumption, every year. The liquid crystal display device has a configuration in which, for example, a backlight (hereinafter, also referred to as BL), a backlight side polarizing plate, a liquid crystal cell, and a viewing-side polarizing plate are provided in this order.
In the flat panel display market in recent years, improvement in saving of power, high definition, and color reproducibility has progressed in order to improve the performance of an LCD, and such improvement has occurred markedly in small-sized tablet PCs, smart phones, and the like. However, development of next-generation high-definition (4K2K, greater than or equal to 100% of EBU ratio) in the present TV standards (FHD: 72% of National Television System Committee (NTSC) ratio≅100% of European Broadcasting Union (EBU) ratio) is also progressing. However, in order, for the next-generation high-definition to become widespread in the market, reduction in costs with functions of members being more integrated in which the number of members is reduced is required.
A method for improving light utilization efficiency of a backlight which is required for saving power has been reviewed. For example, JP2012-169271A discloses a method for realizing high luminance and improving color reproducibility by realizing white light by emitting emission line light (blue light, green light, and red light with a small FWHM) of RGB using a quantum dot (hereinafter, also referred to as QD) which emits red light and green light, as a fluorescent body, between a blue LED and a light guide plate.
In SID'12 DIGEST, p. 895, a method in which light conversion sheets using a quantum dot enhancement film (QDEF) are combined in order to improve color reproducibility of an LCD is proposed.
In addition, devices for improving transmittance have been reviewed in order to improve light utilization efficiency of an optical film member used for a liquid crystal display device. For example, in JP2005-96108A, a method for achieving both of high total light transmittance and high barrier properties by adjusting the film thickness of each layer of barrier films, which are used for an optical member or the like of a FPD and have a substrate, a first inorganic layer, an organic film, and a second inorganic film in this order, is proposed.